The units of an item available for sale during the year were as follows: Jan 1 Inventory 27 units at $120 Feb 17 Purchase 54 units at $138 July 21 Purchase 63 units at $156 Nov 23 Purchase 36 units at $165 There are 50 units of the item in the physical inventory at December 31. The periodic inventory system is used. a. Determine the inventory cost by the first-in, first-out method. $ b. Determine the inventory cost by the last-in, first-out method. $ c. Determine the inventory cost by the average cost method. $